#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
const int MAXN = 3e5 + 10;
const int MOD = 1e9 + 7;
#define int long long
int rnd(int x, int y) { // random number generator
int u= uniform_int_distribution<int>(x, y)(rng); return u;
}
void solve(int tc) {
int N, L;
cin >> N >> L;
int x[N+2], t[N+1];
x[0] = 0, x[N+1] = L;
for(int i=1; i<=N; i++) {
cin >> x[i];
}
for(int i=1; i<=N; i++) {
cin >> t[i];
}
int dp[N+1][N+1][2][N+1];
for(int i=0; i<=N; i++) {
for(int j=0; j<=N; j++) {
for(int k=0; k<2; k++) {
for(int l=0; l<=N; l++) {
dp[i][j][k][l] = 1e18;
}
}
}
}
dp[0][0][0][0] = dp[0][0][1][0] = 0;
for(int i=0; i<=N; i++) {
for(int j=0; j<=N; j++) {
if(i + j > N) continue;
// k = 0
for(int l=0; l<=N; l++) {
// get
if(l>0) {
int hm = 1e18;
if(i > 0) {
hm = min(hm, dp[i-1][j][0][l-1] + x[i] - x[i-1]);
hm = min(hm, dp[i-1][j][1][l-1] + L - x[N+1 - j] + x[i]);
}
if(i > 0 && hm <= t[i]) {
dp[i][j][0][l] = min(dp[i][j][0][l], hm);
}
hm = 1e18;
if(j > 0) {
hm = min(hm, dp[i][j-1][0][l-1] + 2 * (x[i] + L - x[N+1 - j]));
hm = min(hm, dp[i][j-1][1][l-1] + x[N+1 - (j-1)] - x[N+1 - j] + L - x[N+1 - j] + x[i]);
}
if(j > 0 && hm <= t[N+1 - j]) {
dp[i][j][0][l] = min(dp[i][j][0][l], hm);
}
}
// no get
if(i>0) {
dp[i][j][0][l] = min(dp[i][j][0][l], dp[i-1][j][0][l] + x[i] - x[i-1]);
dp[i][j][0][l] = min(dp[i][j][0][l], dp[i-1][j][1][l] + L - x[N+1 - j] + x[i]);
}
if(j>0) {
dp[i][j][0][l] = min(dp[i][j][0][l], dp[i][j-1][0][l] + 2 * (x[i] + L - x[N+1 - j]));
dp[i][j][0][l] = min(dp[i][j][0][l], dp[i][j-1][1][l] + x[N+1 - (j-1)] - x[N+1 - j] + L - x[N+1 - j] + x[i]);
}
}
//k = 1
for(int l=0; l<=N; l++) {
// get
if(l>0) {
int hm = 1e18;
if(i > 0) {
hm = min(hm, dp[i-1][j][0][l-1] + x[i] - x[i-1] + x[i] + L - x[N+1 - j]);
hm = min(hm, dp[i-1][j][1][l-1] + 2 * (L - x[N+1 - j] + x[i]));
}
if(i > 0 && hm <= t[i]) {
dp[i][j][1][l] = min(dp[i][j][1][l], hm);
}
hm = 1e18;
if(j > 0) {
hm = min(hm, dp[i][j-1][0][l-1] + x[i] + L - x[N+1 - j]);
hm = min(hm, dp[i][j-1][1][l-1] + x[N+1 - (j-1)] - x[N+1 - j]);
}
if(j > 0 && hm <= t[N+1 - j]) {
dp[i][j][1][l] = min(dp[i][j][1][l], hm);
}
}
// no get
if(i>0) {
dp[i][j][1][l] = min(dp[i][j][1][l], dp[i-1][j][0][l] + x[i] - x[i-1] + x[i] + L - x[N+1 - j]);
dp[i][j][1][l] = min(dp[i][j][1][l], dp[i-1][j][1][l] + 2 * (L - x[N+1 - j] + x[i]));
}
if(j>0) {
dp[i][j][1][l] = min(dp[i][j][1][l], dp[i][j-1][0][l] + x[i] + L - x[N+1 - j]);
dp[i][j][1][l] = min(dp[i][j][1][l], dp[i][j-1][1][l] + x[N+1 - (j-1)] - x[N+1 - j]);
}
}
}
}
for(int i=N; i>=0; i--) {
for(int j=0; j<=N; j++) {
for(int k=0; k<=N; k++) {
for(int l=0; l<2; l++) {
if(dp[j][k][l][i] != 1e18) {
cout << i << "\n";
return;
}
}
}
}
}
}
int32_t main(){
ios::sync_with_stdio(0); cin.tie(0);
int t = 1; //cin >> t;
for(int i=1; i<=t; i++) solve(i);
}
